The present invention relates to a mobile communication system. Particularly, it relates to a paging technology for calling a mobile unit within the mobile communication system.
As the requirements requested for a mobile unit in the mobile communication system, a significant importance is placed on a longer operating life of its battery in addition to the excellence in its design and operability. Therefore, it is a problem how the communication mechanism should be constructed in order to suppress the battery consumption. For example, in the present mobile communication system, the battery consumption is suppressed as follows: in the case of no data communications with a base station, the mobile unit moves in a mode where the mobile unit receives only the notification information from the base station without two-way communication (standby mode).
In the case where incoming data has occurred for a mobile unit in the standby mode, the mobile communication system cannot recognize where the mobile unit exists. Accordingly, it is required to transmit the incoming signal to the mobile unit from a plurality of base stations within whose cells the mobile unit may exist. Transmitting incoming signals to a mobile unit from a number of base stations in this way, however, results in a waste of the wireless resources. The 3GPP (3rd generation partnerships) 3GPP TS 24. 301 V8. 0. 05. 6. 2 Paging Procedure, and the 3GPP (3rd generation partnerships) 3GPP TS 23. 401 V8. 4. 05. 3. 4. 3 Network Triggered Service Request indicate a location registration technology for narrowing down base stations within whose cells the mobile unit may exist to ones within a certain area in order to suppress the waste of the wireless resources due to the incoming signals. The 3GPP TS 24. 301 V8. 0. 05. 6. 2 Paging Procedure, and the 3GPP TS 23. 401 V8. 4. 05. 3. 4. 3 Network Triggered Service Request are the standard documents that describe technical specifications in the LTE (Long Term Evolution) system, i.e., 3.9 G next-generation wireless communications technology.
The 3GPP TS 24. 301 V8. 0. 05. 6. 2 Paging Procedure, and the 3GPP TS 23. 401 V8. 4. 05. 3. 4. 3 Network Triggered Service Request describe the location registration scheme that uses a tracking area (TA) covered by a group of base stations. A call-processing control apparatus identifies the TA using an area identifier of TAI (Tracking Area Identity). The TAI is allocated to every base station or cell, and one and the same value of the TAI can be assigned to a plurality of base stations or cells. The tracking area within which the mobile unit exists is managed using the TAI.
In the case where a mobile unit is managed within a tracking area, the mobile unit is not required to perform the location registration as long as the mobile unit exists within the tracking area, and thus performs no location registration. In the case where the mobile unit has moved between the tracking areas, the mobile unit performs the location registration. When the mobile unit is managed within a tracking area, an area (hereinafter referred to as a “paging area”) where paging messages for incoming data should be transmitted is only the tracking area. As a result, it becomes possible to suppress the consumption of the wireless resources used to transmit paging messages for incoming data. As described above, however, the mobile unit is required to perform the location registration processing every time the mobile unit moves into another different tracking area, and thus the consumption of the wireless resources increases due to the location registration processing. As a scheme for suppressing the increase in the consumption of the wireless resources due to the location registration processing, the 3GPP TS 24. 301 V8. 0. 05. 6. 2 Paging Procedure and the 3GPP TS 23. 401 V8. 4. 05. 3. 4. 3 Network Triggered Service Request describe a method of managing mobile units using a tracking-area-identity list (TAI list) including a plurality of TAIs.
The use of the TAI list including the plurality of TAIs makes it unnecessary for the mobile unit to perform the location registration processing as long as the mobile unit moves within an area (hereinafter referred to as “tracking-area-based paging area”) including tracking areas that correspond to the plurality of TAIs in the TAI list. At this time, in the case where the mobile unit has been belonging to the tracking-area-based paging area and has been performing no communications for a long time, the call-processing control apparatus cannot judge whether the mobile unit is in the standby mode, or in a mode where the mobile unit cannot communicate with the base stations (for example, where the mobile unit enters a tunnel or underground, and thus cannot receive even the notification information from the base stations; and where the mobile unit turns off the power-supply in the above-described mode, and thus cannot communicate with the base stations without even notifying the base stations and the call-processing control apparatus that the mobile unit has turn off the power-supply). If the mobile unit is in the mode where the mobile unit cannot communicate with the base stations, the call-processing control apparatus executes a processing of deleting the call information for the mobile unit in order to make an effective use of its own memory capacity. Meanwhile, if the mobile unit is in the standby mode, the mobile unit may communicate with the base stations later, and thus the call-processing control apparatus does not delete the call information for the mobile unit. The mobile unit performs the location registration processing periodically in order to allow the call-processing control apparatus to check the mode of the mobile unit. The mobile unit has a periodic timer for performing the location registration periodically. The mobile unit performs the location registration processing when the timer expires, and the timer restarts after the location registration processing is over. As long as the mobile unit executes the location registration using the periodic timer (hereinafter referred to as “periodic timer location registration”), the call-processing control apparatus judges that the mobile unit is in the standby mode. Otherwise, the apparatus judges that the mobile unit is in the call disconnecting mode.
When receiving notification of incoming data for the mobile unit in the standby mode from a gateway, the call-processing control apparatus starts a processing of notifying the mobile unit of receiving incoming data. The notification of incoming data is sent to all of the base stations within the tracking-area-based paging area.
In addition to the above-described documents, there exists JP-A-2008-182507, which discloses a technology for reducing the consumed power in a terminal connectable to both of a broadband wireless communication network and a wireless LAN. The technology is as follows: a connection-information providing apparatus connected to the terminal via the broadband wireless communication network or the wireless LAN stores, in advance, connection information indicating an access point of the wireless LAN together with location information, to provide the terminal with the connection information corresponding to the location of the terminal. Finally, the terminal determines an operation period based on the location of the terminal itself and the provided connection information, and then performs an operation to detect the access point of the wireless LAN.